FIG. 11 is a cross-sectional view of a conventional soldering iron 50 in a disassembled state. The conventional soldering iron 50 has an insert pipe 51 for coupling a heater 52 to a sleeve 53 which has a protruding tip 54. The heater 52 is removeably inserted into the sleeve 53 so that heat from the heater is conducted to the tip 54. The insert pipe 51 is positioned between the sleeve 53 and the heater 52; when in position a gap is formed between the sleeve 53 and the heater 52. This gap inhibits thermal heat from conducting from the heater 52 to the sleeve 53, resulting in poor thermal efficiency. After a period of use, oxidization may form near the gap due to high temperature around the gap. This in turn may cause the sleeve 53 to erode due to oxidization. The oxidization in the gap further reduces the thermal efficiency of the soldering iron 50.
Another shortcoming of the conventional soldering iron 50 is that once the tip 54 becomes worn, the sleeve 53 has to be replaced with the tip. In addition, in situations where the heating tip 54 and the heater 52 are bonded together due to oxidization, it may be necessary to replace the heating tip 54 and the heater 52.
The conventional soldering irons may also have a temperature sensor that is positioned away from the tip so that there is a time lag or delay in measuring the temperature of the tip by the temperature sensor. To compensate for the delay, the conventional soldering irons use expensive control devices, such as proportional, integral, derivative (PID) devices, to control the temperature of the tip. The delay also makes the conventional soldering iron inefficient because when the conventional soldering iron is initially turned on, the heater generates excess heat above the desired set temperature value. That is, the control device continues to provide power to the heater because the temperature sensor is slow to measure the rise in temperature near the tip. As a result, the actual temperature near the tip exceeds the desired temperature. Because of the excess heat generated by the heater, the handle is made longer so that the user may more comfortably hold the handle.